Programmed machine with malfunction detection and control apparatus



June 23, 1964 W. N. BORGER ETAL PROGRAMMED MACHINE WITH MALFUNCTIONDETECTION AND CONTROL APPARATUS Original Filed Nov. 12, 1957SYNCHRONIZER CYCLE SIGNAL RECORDING AND PLAYBACK DEVICE PRODUCTIONNORMAL lNVENTORS 4 44 752 4/. BOPA-TP, 400/54 FP0/I/J46W,

DIFFERENTIAL OR STANDARD OPERATION RECORD SENSITIVITY CONTROL 6224.424Maw/mag day/u @AiA/Z,

fZ-z /x Z 4462 755202; Ww 4770P/VEV United States Patent 3,138,750PROGRAMMED MACHINE WITH MALFUNCTION DETECTION AND CONTROL APPARATUSWalter N. Eorger, Minneapolis, Minn., Louis A. Frohbach, Florence,Mass., Gerald A. Knoblauch, Torrance, Califl, John 0. Lenz, Minneapolis,Minn, and Felix L. Mertesdorf, Arcadia, Calif., assignors toMinneapolis- Honeywell Regulator Company, Minneapolis, Minn, acorporation of Delaware Continuation of application Ser. No. 695,902,Nov. 12, 1957. This application Nov. 17, 1959, Ser. No. 853,515

2 Claims. (Cl. 318-162) The present application is a continuationapplication of the application for Walter N. Borger et al., Serial No.695,902 filed November 12, 1957 entitled Control Apparatus, nowabandoned.

The present invention is concerned with an improved machine controlsystem wherein a recording is made of the variations in a machineoperating condition throughouta complete cycle of a normal or standardoperation. During subsequent production operating cycles, the variationsin the machine operating condition are compared with the recordedmachine operating condition. Variations and deviations between thestandard operation and the production operation are. detected.

.With the increase in automatic machinery there is a constant need forimproved means for sensing deviations from the normal or standardoperation of an automatic machine. Whileit is possible to check theproduct or piece which the machine produces by quality control methods,this .does not alleviate the condition where something happens duringthe production cycle which if allowed to continue would cause seriousdamage.

In the present invention, a responsive device records a machineoperating condition signal throughout a standardcycleof operation. Forsubsequent cycles of the machine operation, the machine operatingcondition signal is compared with the recorded condition signal takenduring the standard operation, and any difference between the twosignals is detected indicating the presenceof a malfunction condition. Afurther improvement is to provide a sensitivity control which isadjusted throughout the operating cycle of the machine to allow fordifferent levels of variation between the standard recorded conditionsignal and the production operating condition signal during differentportions of the total operating cycle of the machine.

An object of the present invention is to provide an improved automaticmachine control for detecting an abnormal operation of a machine.

Another object of the present invention is to provide a machine controlfor determining a malfunction in the ma chine operation in which astandard operation condition is compared with a production operationcondition and any deviation is sensed.

And'still another object of the present invention is to provide in amachine control system a means of recording a variation in a motoroperating condition throughout a normal operation cycle and when themachine operating condition variations of subsequent operating cycles ofthe machine vary from'the normal more than a predetermined amount,abnormal operation of the machine is detected.

These and other objects will become apparent upon a study of thefollowing specification and drawing of which a single figure is a blockdiagram of the present invention.

Referring to the single figure a machine is driven by a drive motor 11.The machine might be any conventional production machine such as anautomatic screw machine which has a number of operations to be performedthroughout a continuous operating cycle. The drive motor being shownschematically as an electric ice motor provides the power for operatingthe machine throughout its cycle. The manner of control for the ma chineis of no concern. Machine 10 might have any type of programming controlapparatus to provide repeating cycles of operation according to somepredetermined schedule. Such independent programming control apparatus,which is not shown, controls the machine through a series of operationsmaking up one cycle of operation. A motor input current sensor ormachine operating con dition responsive device 12 responds to variationsin the input current to motor 11. The machine operating conditionresponsive device could very well be a device responsive to torque,hydraulic fluid pressure, sound, and other conditions of machineoperation which vary depending upon the operating condition of themachine. For explanation purposes the invention is disclosed with amotor input current sensor which senses the variations in the motorcurrent as the load on the motor varies with the load on the machine.

An output of the motor current sensor is fed into a conventionalamplifier 13 to amplify the relatively small signal of motor conditionsensor 12. The amplifier output is connected through one switch 14 of agang operated bank of switches 15 to a signal recording and playbackdevice 20. When the main control lever 21 of the gang switches is in thestandard record position switch 14 is closed. The recording and playbackdevice is a conventional type such as a magnetic tape or wire forrecording the variations in the amplified motor operating conditionsignal throughout the operating cycle of the machine 10. When the gangswitch lever 21 is in the standard record position the signal recordingand playback device is in the record position so that the signal outputof the amplifier is recorded. Connected to be in synchronism with theoperating cycle of machine 10 is a cycle synchronizer 22 which insuresthat the signal recording and playback device will start at its initialposition or at the beginning of the record each time the machine 10begins an operating cycle.

' Let us assume that a standard or normal operation of the machine istaking place as determined by an independent program control apparatuswhich is not shown. In the case of an automatic screw machine a piece ofmaterial would be inserted in the machine either manually orautomatically and the machine would be started to operate through onecomplete cycle as determined by the programming control apparatus.During this operating cycle, the variations in the machine operatingcondition or motor input current are recorded by signal recording device20. In the case of an automatic screw machine, during one operation ofthe complete programmed cycle, there may be a heavy load and the outputof sensor 12 might be large, while during another operation of the cycleof machine 10, the load may be small reducing the output of sensor 12.These variations in output of sensor 12 are recorded throughout thecomplete programmed operating cycle of machine 10 to produce a normal orstandard record of the motor operating condition variation. Of course,during the making of this standard record the machine would be checkedvery closely by a machine operator, and after the cycle was completed,the production piece whatever it 'might be would be checked to determinewhether a satisfactory standard record was obtained.

After the standard record was obtained, lever 21 is thrown to the rightto the production operation. This transfers the device 20 from recordingto playback and also the playback output of device 20 connected throughswitch 23 to one of the inputs of a differential signal sensor 24. Atthe same time the output of amplifier 13 is disconnected from the device20 and is connected through switch 25 to a second input of theditferential sig- '2 a nal sensor. The differential signal sensor is ofa conventional type having means for receiving two signals and having anoutput depending upon the deviation or difference between these inputsignals.

With the lever 21 in the production. operation position, the machine isstarted on its normal production operation under the control of theindependent programmed control apparatus. Each time it began a cycle ofoperation, the cycle synchronizer initiates the operation of theplayback device so that simultaneously the standard record of machineoperating condition which was previously made and the present variationsin machine operating condition throughout the programmed operating cycleare fed into the differential signal sensor.

Connected to the differential signal sensor is a sensitivity control 30and a signal device or sensor 31. By means of the sensitivity control, apredetermined portion of the differential between the standard signaland the present production signal is selected, and if the predeterminedportion signal exceeds some predetermined value, the device 31 isenergized to give an appropriate response.

While in the production operation let us assume that during the drillingoperation of the automatic screw machine, a tool became dull and themotor load increased. This would produce a motor operating condition orinput current considerably different from the standard operation. Thedifferential signal sensor senses this deviation. When the output ofsensor 24 exceeds the predetermined amount selected by the sensitivitycontrol, sensor device 31 is operated to sound a signal or turn off themachine.

The sensitivity control is connected into the motor drive of themachine; so that, during the machine operating cycle, the sensitivitycontrol is adjusted to provide for different levels of sensitivity. Thusdifferent levels of deviations of the production operation motoroperation signal and standard signal can be selected to cause operationof signal device 31. This is quite important in certain operations ofthe machine such as during a roughing operation where the character ofthe material being worked on changes the motor load considerably. As theroughing operation is not critical, a larger variation is selected, andthe differential signal sensor output could be quite high before anyoutput would be available to device 31. As the machine operationcontinued to some other type of operation such as a finishing operation,the motor load is more critically controlled by making the sensitivitycontrol very sensitive by using a large portion of the output of sensor24. A small differential between the signals fed into the sensor 24would then bring about operation of device 31.

The present invention readily detects a number of malfunction conditionsoccurring in an automatic machine and greatly increases the automaticmachine productivity. Furthermore the amount of scrap is reduced andtool breakage is minimized. In any automation program Where theelimination of manpower and the provision of a machine which willoperate continuously to produce high quality products, an invention ofthis type is of great importance.

While the invention has been disclosed in one particular manner thereare other obvious modifications which would be apparent to one skilledin the ant. Therefore it is intended that the present invention belimited only by the scope of the appended claims in which I claim:

1. In a malfunction sensing device for use with a machine havingselected mode of operation determined by an independent controller,machine operating condition responsive means responsive to variations ina machine operating condition which is indicative of the load on themachine throughout an operating cycle of the machine as determined bythe independent controller, recording means, means selectivelyconnecting said responsive means to said recording means to record thevariations in a first output of said responsive means occurringthroughout one complete scheduled cycle of operation of the machine whenit is operating in a normal manner, playback means for playing back in arepeat fashion said recorded output of said responsive means duringsubsequent normal scheduled operation cycle of the machine, differentialsensing means, means connecting said recorded output of said playbackmeans and said first output of said responsive means to saiddifferential sensing means during subsequent scheduled operations of themachine so that the variations in said first and said recorded outputsare compared and any deviation sensed, malfunction signal means, andmeans connecting said malfunction signal means to said differentialsensing means so that when the difference between said first output ofsaid responsive means during a subsequent operation and said recordedoutput of said responsive means during the standard operation is above apredetermined value said signal means functions in a manner indicativeof a malfunction condition, and means for varying said predeterminedvalue throughout said operating cycle of the machine in accordance witha predetermined schedule.

2. In a malfunction sensing device for an automatic machine having aselected schedule of operation which is determined by an independentcontroller, machine operat ing condition responsive means, saidcondition being indicartive of the load of the machine, recording means,means selectively connecting said responsive means to said recordingmeans to record the variations in an output of said responsive meansoccurring throughout one cycle of the selected schedule of operation ofthe machine when it is operating in a normal manner under the control ofthe controller, playback means for playing back in a repeat fashion therecorded output of said responsive means during the normal operationcycle of the machine, differential sensing means, means connecting anoutput of said playback means and said output of said responsive meansto said differential sensing means during an operating cycle of themachine on subsequent operations so that the variations in the output ofsaid responsive means during the normal operating cycle and thesubsequent cycles of the machine are compared and any deviation sensed,sensor means connected to said differential sensing means to beresponsive to a predetermined difference in the normal recorded outputand the subsequent operating output for providing a signal indicative ofthe presence of an abnormal condition, and means associated with saidsensor means and scheduled by the controller for resetting saiddetection means to vary said predetermined difference needed to producesaid signal throughout an operating cycle of the machine in accordancewith a prearranged schedule synchronized with the machine operation.

References Cited in the file of this patent UNITED STATES PATENTS2,493,543 Merchant Jan. 3, 1950 2,537,770 Livingston Jan. 9, 19512,866,145 Peaslee et al Dec. 23, 1958

1. IN A MALFUNCTION SENSING DEVICE FOR USE WITH A MACHINE HAVINGSELECTED MODE OF OPERATION DETERMINED BY AN INDEPENDENT CONTROLLER,MACHINE OPERATING CONDITION RESPONSIVE MEANS RESPONSIVE TO VARIATIONS INA MACHINE OPERATING CONDITION WHICH IS INDICATIVE OF THE LOAD ON THEMACHINE THROUGHOUT AN OPERATING CYCLE OF THE MACHINE AS DETERMINED BYTHE INDEPENDENT CONTROLLER, RECORDING MEANS, MEANS SELECTIVELYCONNECTING SAID RESPONSIVE MEANS TO SAID RECORDING MEANS TO RECORD THEVARIATIONS IN A FIRST OUTPUT OF SAID RESPONSIVE MEANS OCCURRINGTHROUGHOUT ONE COMPLETE SCHEDULED CYCLE OF OPERATION OF THE MACHINE WHENIT IS OPERATING IN A NORMAL MANNER, PLAYBACK MEANS FOR PLAYING BACK IN AREPEAT FASHION SAID RECORDED OUTPUT OF SAID RESPONSIVE MEANS DURINGSUBSEQUENT NORMAL SCHEDULED OPERATION CYCLE OF THE MACHINE, DIFFERENTIALSENSING MEANS, MEANS CONNECTING SAID RECORDED OUTPUT OF SAID PLAYBACKMEANS AND SAID FIRST OUTPUT OF SAID RESPONSIVE MEANS TO SAIDDIFFERENTIAL SENSING MEANS DURING SUBSEQUENT SCHEDULED OPERATIONS OF THEMACHINE SO THAT THE VARIATIONS IN SAID FIRST AND SAID RECORDED OUTPUTSARE